A Test of Two-photon Entanglement in Spatial Modes

Radhika Prasad, Nilakshi Senapati, Abhinandan Bhattacharjee +2 more

Robert Fickler, Mario Krenn, Radek Łapkiewicz +4 more

Complex transverse spatial modes of photons are very interesting for both, foundations and applications of quantum information. In a first experiment, we generate two-dimensional bi-partite entanglement where each photon carries an orbital angular momentum of a quantum number up to 300. Secondly, we demonstrate (100 × 100)-dimensional entanglement, using again the spatial modes of photons and a novel nonlinear criterion which uses only information about two-dimensional subspace correlations. In a third test, we increase the complexity of the state by entangling ”vector photons” that show a transverse varying polarization. Thereby, we demonstrate a surprising property: Such photons can be both entangled and not entangled in polarization depending on their transverse spatial position.

Hugo Defienne, Matthew C. Reichert, Xiaohang Sun +1 more

Sumant S. R. Oemrawsingh, J. A. de Jong, Xuan Ma +4 more

By analyzing entangled photon states in terms of high-dimensional spatial mode superpositions, it becomes feasible to expose high-dimensional entanglement, and even the nonlocality of twin photons. To this end, a proper analyzer should be designed that is capable of handling a large number of spatial modes, while still being convenient to use in an experiment. We compare two variants of a high-dimensional spatial mode analyzer on the basis of classical and quantum considerations. These analyzers have been tested in classical optical experiments.

Yoon-Ho Kim

Adam Vallés, Vincenzo D’Ambrosio, Martin Hendrych +4 more

We demonstrate a scheme to generate noncoherent and coherent correlations, i.e., a tunable degree of entanglement, between degrees of freedom of a single photon. Its nature is analogous to the tuning of the purity (first-order coherence) of a single photon forming part of a two-photon state by tailoring the correlations between the paired photons. Therefore, well-known tools such as the Clauser-Horne-Shimony-Holt (CHSH) Bell-like inequality can also be used to characterize entanglement between degrees of freedom. More specifically, CHSH inequality tests are performed, making use of the polarization and the spatial shape of a single photon. The four modes required are two polarization modes and two spatial modes with different orbital angular momentum.